1. Technical Field
The present invention relates to a chain for a chain-type continuously variable transmission, and more particularly to a structure of the chain.
2. Background Art
There are known continuously variable transmissions including two pulleys each having conical surfaces that face each other, the distance therebetween being variable, and a flexible endless member which is wound around the two pulleys. The rotation of one pulley is transmitted to the other pulley through the flexible endless member. At this time, by changing the distance between the conical surfaces, it is possible to change the winding radius of the flexible endless member with respect to the pulley, thereby allowing the transmission ratio to change. Japanese Patent No. 3,477,545 discloses a chain for use as a flexible endless member of a continuously variable transmission.
This chain is formed by arranging a plurality of chain elements in a circumferential direction and interconnecting them. Each chain element includes plate-shaped links having openings at respective end of the link, and a pin and an inter-piece both passing though each of the openings. Each link is positioned along the chain circumferential direction. Further, a plurality of links are arranged in the width direction of the chain, and these links, pin, and inter-piece constitute one element. The pins and the inter-pieces pass through the links arranged in the width direction. Both ends of the pin come into contact with the conical surfaces of the pulley. The chain elements that are adjacent to each other are interconnected by allowing the pin or the inter-piece of one chain element of the adjacent chain elements to pass through the opening of the other chain element. Power is transmitted between the chain elements via contact surfaces of the pin and the inter-piece. The pin and the inter-piece rotate on the contact surfaces and come into contact with each other, thereby allowing the chain to bend.
Japanese Patent No. 3,477,545 also discloses suppressing vibration (chordal action) of a linear portion of the chain wound around two pulleys. It describes that this vibration is partly caused by up and down movement of the pin, which is located on the boundary between the linear portion of the chain and the arc-like portion in the pulley, when the pin moves in an arc motion as the pulley rotates (see paragraph 0012). This movement of the pin produces up and down movement of the linear portion. Japanese Patent No. 3,477,545 further discloses that vibration is also partly caused by rapid change of the direction along which the pin moves to enter the pulley after the pin first contacts the pulley (see paragraphs 0013 and 0014).
It also suggests that, in order to reduce above-described vibration of the linear portion, a position at which the pin first contacts the pulley is set at a higher position (paragraph 0016). The tension acts on the chain to generate a force couple, and this force couple acts to lift the subsequent element of the adjacent chain elements. Thus, a position at which the pin first contacts the pulley when it enters the pulley is set at the highest position or a position near that position; that is, a position on the outer side of the pulley in the radial direction or a position near that position.